Background: Continuous Ambulatory Peritoneal dialysis (CAPD) has been promoted to be the main method of treatment for Thai End-Stage Renal Disease (ESRD) patients; however, a national survey of dialysis centers reported an annual incidence of black-stained particle of 57.6 per 1,000 CAPD cases. The objective of this study was to identify potential causes of the stain in the nurse practitioners’ prospect. Findings: This study applied three-round Delphi technique. In the first round, the questionnaire was sent to 127 nurses in all dialysis centers. Their responses were analyzed to come up with an anonymous summary, which was presented in the second and third round of the survey among 80 and 200 nurses. The response rates of the three rounds of Delphi were 57.5%, 81.3%, and 75.0%, respectively. Nurses consistently believed that the contamination was caused by spilled-out povidone-iodine solution during transfer set change. Other potential causes were previous peritonitis, inadequate dialysis, low serum albumin, transfer set soaking with antiseptics, patient history of diabetes, dressing technique, and existence of dry abdomen period. Conclusions: Black-stained particle is a common contamination of dialysis tube in CAPD patients. This study proposed some potential determinants, most of which were relevant to care process.